Hydraulic pillar-type rotary cranes, particularly for motor trucks



May 22, 1962 D L. REHNsTRb'M 3,035,711

HYDRAULIC PILLAR TYPE ROTARY CRANES, PARTICULARLY FOR MOTOR TRUCKS FiledMay 18, 1959 11th ennui-b lpefrzsbfim IN VE N TOR BT ORNEYS UnitedStates Patent 3,035,711 HYDRAULIC PILLAR-TYPE ROTARY CRANES,PARTICULARLY FOR MOTOR TRUCKS Dick Lennart Rehnstrtim, Skelleftea,Sweden, assignor to Fabriks AB Forslund & Co., Skelleftea, Sweden FiledMay 18, 1959, Ser. No. 814,027 Claims priority, application Sweden May20, 1958 3 Claims. (Cl. 212-35) The present invention relates to cranesparticularly for use on motor trucks and of the type comprising a pillarand a boom swingable relative to the pillar both vertically andhorizontally, and whose angular movement in the vertical sense isefiected, in part at least, by a hydraulic motor comprising a fluidpower cylinder and an associated power piston, said piston beingarranged to act on the boom near the inner end thereof which is pivotedto the pillar, and the boom being provided with an extension arm at itsouter end which is vertically swingable by a second power cylinder andan associated power piston.

The invention has for its object to provide for a considerably largerrange of angular movement of the extension arm than could be attainedwith prior-art cranes of this kind, and particularly to enable theboom-extension arm to be moved into an angular position above thelongitudinal axis of the boom.

This has been realized, according to the main features of the invention,by connecting the second power cylinder-and-piston device to theextension arm through the intermediary of an auxiliary arm which iseither rigidly or pivotally connected to the tiltable extension arm, theextension arm and the boom being so designed as to enable the anglethrough which the extension arm is movable relative to the boom, to bevery wide. This can be best accomplished by forming the tiltableextension arm and/or the boom with a forked end adjacent the pivot shaftinterconnecting the same, as well as by constituting this pivot shaft astwo separate trunnions between which said second power cylinder or itspiston rod, respectively, is accommodated and may pass freely.Preferably both the boom and its extension arm, in a manner known perse, are invertedly channel-shaped in cross-section.

Two embodiments of the invention will be described hereinafter by way ofexample with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic elevation of a crane according to the firstembodiment of the invention in which the auxiliary arm is pivotallyconnected to the tiltable boom extension arm;

FIG. 2 similarly shows a diagrammatic elevation of a crane according tothe second embodiment of the invention in which the auxiliary arm isrigidly connected to the tiltable boom extension arm.

In both figures of the drawing, the crane is illustrated as mounted on aheavy-duty truck, parts of the chassis, load-carrying platform anddrivers cabin of this truck being indicated in the drawing. Numeral 1designates the stand or pillar of the crane, this pillar being suitablyin the form of a large-diameter tube serving at the same time as a powercylinder forming part of the hydraulic motor by which the boom 4 isswingable in the vertical sense. The pivoting of the boom in thehorizontal sense is elfected by means not illustrated in detail in thedrawing. The top end of the pillar 1 is terminated by a rotatablesupporting arm 2 which is angularly curved and which carries at itsextreme end a horizontal pivot shaft 3 for the boom 4. Numeral 5designates a point of articulation for the piston rod of the hydraulicmotor housed within the pillar 1. The apparatus further comprises avertically swingable boom extension arm, or tilting arm, 6 which isactuated by means of a second hydraulic motor comprising a hydraulicpower cylinder 7 articulated to the boom 4, and a piston rod 8 theextreme end of which is articulated to a pivot shaft 9 serving also tomount one end of the auxiliary arm 16 associated with the tiltable boomextension arm 6. The extension arm 6 is mounted on a horizontal pivotpin 11 for pivotal movement relative to the boom.

In the embodiment shown in FIG. 1, the auxiliary arm 10 is pivotallyconnected to the tiltable extension arm 6, being mounted on a horizontalpivot pin 12 thereon. In addition, a link 13 is provided having one endmounted on the pivot shaft 9, in common with the piston rod 8 and theauxiliary arm 10, while its opposite end is mounted on a pivot pin 14secured to the boom 4. It is obvious that, by designing the boom and thetiltable extension arm in the manner indicated in the preamble of thisspecification, it is possible to attain a very wide range of elevationangles for the extension arm. In particular, it will be possible also tomove the tiltable boom extension arm into angular positions above thelongitudinal axis of the boom, thereby highly increasing the maximumlifting height of the crane and thus also its applicability. The brokenlines indicate the positions of the various components in the retractedposition of the boom assembly of the crane.

The embodiment shown in FIG. 2 is slightly simplified in that the items12, 13 and 14 are dispensed with and the auxiliary arm 10 is rigidly,rather than pivotally, connected with the tilting boom extension arm 6.Obviously, the advantages above referred to will be obtained in thisconstruction also, since auxiliary arm 1% extends sufficiently below theboom extension arm 6 to permit the piston rod 8 to clear pivot 11throughout a substantial upward angular movement of arm 6 above thelongitudinal axis of the main boom 4. Moreover if as previouslymentioned, pivot shaft 11 is constituted by two separate trunnionsspaced to clear the piston rod the range of movement is even greater.The boom extension is shown articulated to the main boom to permit suchrange of hinging and this is facilitated in FIGURE 2 by cutting back theweb of the extension whose flanges straddle those of the main boom, forclearance purposes.

The invention is not restricted to the embodiments here illustrated butmay be varied in many respects without departing from the scope of theappended claims.

What is claimed is:

1. In a crane adapted for use on heavy-duty motor trucks and the like,in combination an upright pillar, a main boom, means pivoting said mainboom near one end thereof adjacent the upper end of said pillar forswinging vertically, a hydraulic cylinder and piston with rod interposedbetween and connected to the pillar and to the main boom adjacent thepivoting means to swing said main boom in a vertical plane, a boomextension for said main boom, means pivoting one end of the boomextension about the free end of the main boom for vertical swinging ofthe boom extension through an are extending both above and below thelongitudinal axis of the main boom, a first link having one endarticulated to said boom extension beyond the means pivoting said boomextension, at second link of greater length than said first link andhaving one end articulated to the free end of the main boom, the freeends of both links being pivotally joined to each other, a secondhydraulic cylinder and piston with rod connected between the main boomand the pivotal joint formed by the free end of the two links wherebythe boom extension is movable hydraulically into position both above andbelow the longitudinal axis of the main boom.

4 2. The invention as described in claim 1 wherein the point where thesecond link is articulated to the free end main boom is of invertedchannel shape to partially of the main boom. house the second hydrauliccylinder, and said means pivoting one end of the boom extension aboutthe free end References Cited in the file of this patent of the mainboom comprises two separate trunnions be- 5 UNITED STATES PATENTS tweenwhich the second hydraulic cylinder and piston rod is accgmmodated HegreJune 10, 3. The invention as described in claim 2 wherein the 2,786,580Balogh 25, 1957 two separate trunnions are spaced downwardly from the2,895,622 Sundin y 21, 1959

